The GeoTextile support type can be used to model the various types of slope reinforcement which are used in the form of meshes, grids, strips, etc. There are a wide variety of such support systems, referred to as geotextiles or geofabrics, geogrids, geosynthetics etc.
Although the term “GeoTextile” actually refers to a specific category of reinforcing materials, for the purpose of the following discussion, the term “GeoTextile” will be used to refer to all forms of flexible planar reinforcement, which are used in the form of fabrics, meshes, grids, strips, membranes, etc, to reinforce slopes. This includes both synthetic (polymer) and metal (e.g. steel strip) reinforcement.
A good starting point to get more information is the Overview of Support Implementation help topic in Slide, which applies to all support models.

How does Slide calculate pullout strength?
For a geotextile, pullout can only occur if the embedded end is NOT anchored. The maximum pullout force which can be mobilized (per unit width of slope) is given by:
where the formulation for shear strength depends on whether the Linear or Hyperbolic strength model is used. See the Implementation of GeoTextile Support in Slide section of the GeoTextile help topic.

What input parameters should be used for pullout adhesion for geotextiles?
The following is a good reference on the evaluation of geotextile interface properties:
Farrag, K., and Morvant, M. J. (2004). Evaluation of Interaction Properties of Geosynthetics in Cohesive Soils: Lab and Field Pullout Tests. Louisiana Transportation Research Center. FHWA/LA.03/380.
On page 74 (Evaluation of Pullout Coefficients) there is a series of equations. Equations 3, 4, and 5 are basically what Slide uses. In equation 5, Ca is the soil adhesion that Slide asks for, and delta is the friction angle. If you look at equation 8 in the above report, you’ll see the definition of alpha and F* and how they relate to pullout resistance. In comparing this equation to equation 5, you’ll see that you can equate the two equations. If you have alpha and F*, set the soil adhesion to zero and the friction angle = invtan(alpha*F*).
These equations are also defined in the GeoTextile section of the Slide online help, where the following topics are addressed:
 Strip coverage
 Tensile strength
 Force application
 Force orientation
 Anchorage
 Pullout strength
 Shear strength considerations
 Implementation of geotextile support in Slide